| // Copyright (c) 2017 The Khronos Group Inc. |
| // Copyright (c) 2017 Valve Corporation |
| // Copyright (c) 2017 LunarG Inc. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| #include "aggressive_dead_code_elim_pass.h" |
| |
| #include "cfa.h" |
| #include "iterator.h" |
| #include "spirv/1.0/GLSL.std.450.h" |
| |
| #include <stack> |
| |
| namespace spvtools { |
| namespace opt { |
| |
| namespace { |
| |
| const uint32_t kTypePointerStorageClassInIdx = 0; |
| const uint32_t kEntryPointFunctionIdInIdx = 1; |
| const uint32_t kSelectionMergeMergeBlockIdInIdx = 0; |
| const uint32_t kLoopMergeMergeBlockIdInIdx = 0; |
| |
| } // namespace |
| |
| bool AggressiveDCEPass::IsVarOfStorage(uint32_t varId, uint32_t storageClass) { |
| const ir::Instruction* varInst = get_def_use_mgr()->GetDef(varId); |
| const SpvOp op = varInst->opcode(); |
| if (op != SpvOpVariable) return false; |
| const uint32_t varTypeId = varInst->type_id(); |
| const ir::Instruction* varTypeInst = get_def_use_mgr()->GetDef(varTypeId); |
| if (varTypeInst->opcode() != SpvOpTypePointer) return false; |
| return varTypeInst->GetSingleWordInOperand(kTypePointerStorageClassInIdx) == |
| storageClass; |
| } |
| |
| bool AggressiveDCEPass::IsLocalVar(uint32_t varId) { |
| return IsVarOfStorage(varId, SpvStorageClassFunction) || |
| (IsVarOfStorage(varId, SpvStorageClassPrivate) && private_like_local_); |
| } |
| |
| void AggressiveDCEPass::AddStores(uint32_t ptrId) { |
| get_def_use_mgr()->ForEachUser(ptrId, [this](ir::Instruction* user) { |
| switch (user->opcode()) { |
| case SpvOpAccessChain: |
| case SpvOpInBoundsAccessChain: |
| case SpvOpCopyObject: |
| this->AddStores(user->result_id()); |
| break; |
| case SpvOpLoad: |
| break; |
| // If default, assume it stores e.g. frexp, modf, function call |
| case SpvOpStore: |
| default: |
| if (!IsLive(user)) AddToWorklist(user); |
| break; |
| } |
| }); |
| } |
| |
| bool AggressiveDCEPass::AllExtensionsSupported() const { |
| // If any extension not in whitelist, return false |
| for (auto& ei : get_module()->extensions()) { |
| const char* extName = |
| reinterpret_cast<const char*>(&ei.GetInOperand(0).words[0]); |
| if (extensions_whitelist_.find(extName) == extensions_whitelist_.end()) |
| return false; |
| } |
| return true; |
| } |
| |
| bool AggressiveDCEPass::KillInstIfTargetDead(ir::Instruction* inst) { |
| const uint32_t tId = inst->GetSingleWordInOperand(0); |
| const ir::Instruction* tInst = get_def_use_mgr()->GetDef(tId); |
| if (dead_insts_.find(tInst) != dead_insts_.end()) { |
| context()->KillInst(inst); |
| return true; |
| } |
| return false; |
| } |
| |
| void AggressiveDCEPass::ProcessLoad(uint32_t varId) { |
| // Only process locals |
| if (!IsLocalVar(varId)) return; |
| // Return if already processed |
| if (live_local_vars_.find(varId) != live_local_vars_.end()) return; |
| // Mark all stores to varId as live |
| AddStores(varId); |
| // Cache varId as processed |
| live_local_vars_.insert(varId); |
| } |
| |
| bool AggressiveDCEPass::IsStructuredIfHeader(ir::BasicBlock* bp, |
| ir::Instruction** mergeInst, |
| ir::Instruction** branchInst, |
| uint32_t* mergeBlockId) { |
| auto ii = bp->end(); |
| --ii; |
| if (ii->opcode() != SpvOpBranchConditional) return false; |
| if (ii == bp->begin()) return false; |
| if (branchInst != nullptr) *branchInst = &*ii; |
| --ii; |
| if (ii->opcode() != SpvOpSelectionMerge) return false; |
| if (mergeInst != nullptr) *mergeInst = &*ii; |
| if (mergeBlockId != nullptr) |
| *mergeBlockId = |
| ii->GetSingleWordInOperand(kSelectionMergeMergeBlockIdInIdx); |
| return true; |
| } |
| |
| void AggressiveDCEPass::ComputeBlock2HeaderMaps( |
| std::list<ir::BasicBlock*>& structuredOrder) { |
| block2headerMerge_.clear(); |
| block2headerBranch_.clear(); |
| std::stack<ir::Instruction*> currentMergeInst; |
| std::stack<ir::Instruction*> currentBranchInst; |
| std::stack<uint32_t> currentMergeBlockId; |
| currentMergeInst.push(nullptr); |
| currentBranchInst.push(nullptr); |
| currentMergeBlockId.push(0); |
| for (auto bi = structuredOrder.begin(); bi != structuredOrder.end(); ++bi) { |
| if ((*bi)->id() == currentMergeBlockId.top()) { |
| currentMergeBlockId.pop(); |
| currentMergeInst.pop(); |
| currentBranchInst.pop(); |
| } |
| block2headerMerge_[*bi] = currentMergeInst.top(); |
| block2headerBranch_[*bi] = currentBranchInst.top(); |
| ir::Instruction* mergeInst; |
| ir::Instruction* branchInst; |
| uint32_t mergeBlockId; |
| if (IsStructuredIfHeader(*bi, &mergeInst, &branchInst, &mergeBlockId)) { |
| currentMergeBlockId.push(mergeBlockId); |
| currentMergeInst.push(mergeInst); |
| currentBranchInst.push(branchInst); |
| } |
| } |
| } |
| |
| void AggressiveDCEPass::ComputeInst2BlockMap(ir::Function* func) { |
| for (auto& blk : *func) { |
| blk.ForEachInst( |
| [&blk, this](ir::Instruction* ip) { inst2block_[ip] = &blk; }); |
| } |
| } |
| |
| void AggressiveDCEPass::AddBranch(uint32_t labelId, ir::BasicBlock* bp) { |
| std::unique_ptr<ir::Instruction> newBranch(new ir::Instruction( |
| context(), SpvOpBranch, 0, 0, |
| {{spv_operand_type_t::SPV_OPERAND_TYPE_ID, {labelId}}})); |
| get_def_use_mgr()->AnalyzeInstDefUse(&*newBranch); |
| bp->AddInstruction(std::move(newBranch)); |
| } |
| |
| bool AggressiveDCEPass::AggressiveDCE(ir::Function* func) { |
| // Compute map from instruction to block |
| ComputeInst2BlockMap(func); |
| // Compute map from block to controlling conditional branch |
| std::list<ir::BasicBlock*> structuredOrder; |
| cfg()->ComputeStructuredOrder(func, &*func->begin(), &structuredOrder); |
| ComputeBlock2HeaderMaps(structuredOrder); |
| bool modified = false; |
| // Add instructions with external side effects to worklist. Also add branches |
| // EXCEPT those immediately contained in an "if" selection construct. |
| // TODO(greg-lunarg): Handle Frexp, Modf more optimally |
| call_in_func_ = false; |
| func_is_entry_point_ = false; |
| private_stores_.clear(); |
| // Stacks to keep track of when we are inside an if-construct. When not |
| // immediately inside an in-construct, we must assume all branches are live. |
| std::stack<bool> assume_branches_live; |
| std::stack<uint32_t> currentMergeBlockId; |
| // Push sentinel values on stack for when outside of any control flow. |
| assume_branches_live.push(true); |
| currentMergeBlockId.push(0); |
| for (auto bi = structuredOrder.begin(); bi != structuredOrder.end(); ++bi) { |
| if ((*bi)->id() == currentMergeBlockId.top()) { |
| assume_branches_live.pop(); |
| currentMergeBlockId.pop(); |
| } |
| for (auto ii = (*bi)->begin(); ii != (*bi)->end(); ++ii) { |
| SpvOp op = ii->opcode(); |
| switch (op) { |
| case SpvOpStore: { |
| uint32_t varId; |
| (void)GetPtr(&*ii, &varId); |
| // Mark stores as live if their variable is not function scope |
| // and is not private scope. Remember private stores for possible |
| // later inclusion |
| if (IsVarOfStorage(varId, SpvStorageClassPrivate)) |
| private_stores_.push_back(&*ii); |
| else if (!IsVarOfStorage(varId, SpvStorageClassFunction)) |
| AddToWorklist(&*ii); |
| } break; |
| case SpvOpLoopMerge: { |
| // Assume loops live (for now) |
| // TODO(greg-lunarg): Add dead loop elimination |
| assume_branches_live.push(true); |
| currentMergeBlockId.push( |
| ii->GetSingleWordInOperand(kLoopMergeMergeBlockIdInIdx)); |
| AddToWorklist(&*ii); |
| } break; |
| case SpvOpSelectionMerge: { |
| auto brii = ii; |
| ++brii; |
| bool is_structured_if = brii->opcode() == SpvOpBranchConditional; |
| assume_branches_live.push(!is_structured_if); |
| currentMergeBlockId.push( |
| ii->GetSingleWordInOperand(kSelectionMergeMergeBlockIdInIdx)); |
| if (!is_structured_if) AddToWorklist(&*ii); |
| } break; |
| case SpvOpBranch: |
| case SpvOpBranchConditional: { |
| if (assume_branches_live.top()) AddToWorklist(&*ii); |
| } break; |
| default: { |
| // Function calls, atomics, function params, function returns, etc. |
| // TODO(greg-lunarg): function calls live only if write to non-local |
| if (!context()->IsCombinatorInstruction(&*ii)) { |
| AddToWorklist(&*ii); |
| } |
| // Remember function calls |
| if (op == SpvOpFunctionCall) call_in_func_ = true; |
| } break; |
| } |
| } |
| } |
| // See if current function is an entry point |
| for (auto& ei : get_module()->entry_points()) { |
| if (ei.GetSingleWordInOperand(kEntryPointFunctionIdInIdx) == |
| func->result_id()) { |
| func_is_entry_point_ = true; |
| break; |
| } |
| } |
| // If the current function is an entry point and has no function calls, |
| // we can optimize private variables as locals |
| private_like_local_ = func_is_entry_point_ && !call_in_func_; |
| // If privates are not like local, add their stores to worklist |
| if (!private_like_local_) |
| for (auto& ps : private_stores_) AddToWorklist(ps); |
| // Add OpGroupDecorates to worklist because they are a pain to remove |
| // ids from. |
| // TODO(greg-lunarg): Handle dead ids in OpGroupDecorate |
| for (auto& ai : get_module()->annotations()) { |
| if (ai.opcode() == SpvOpGroupDecorate) AddToWorklist(&ai); |
| } |
| // Perform closure on live instruction set. |
| while (!worklist_.empty()) { |
| ir::Instruction* liveInst = worklist_.front(); |
| // Add all operand instructions if not already live |
| liveInst->ForEachInId([this](const uint32_t* iid) { |
| ir::Instruction* inInst = get_def_use_mgr()->GetDef(*iid); |
| if (!IsLive(inInst)) AddToWorklist(inInst); |
| }); |
| // If in a structured if construct, add the controlling conditional branch |
| // and its merge. Any containing if construct is marked live when the |
| // the merge and branch are processed out of the worklist. |
| ir::BasicBlock* blk = inst2block_[liveInst]; |
| ir::Instruction* branchInst = block2headerBranch_[blk]; |
| if (branchInst != nullptr && !IsLive(branchInst)) { |
| AddToWorklist(branchInst); |
| AddToWorklist(block2headerMerge_[blk]); |
| } |
| // If local load, add all variable's stores if variable not already live |
| if (liveInst->opcode() == SpvOpLoad) { |
| uint32_t varId; |
| (void)GetPtr(liveInst, &varId); |
| ProcessLoad(varId); |
| } |
| // If function call, treat as if it loads from all pointer arguments |
| else if (liveInst->opcode() == SpvOpFunctionCall) { |
| liveInst->ForEachInId([this](const uint32_t* iid) { |
| // Skip non-ptr args |
| if (!IsPtr(*iid)) return; |
| uint32_t varId; |
| (void)GetPtr(*iid, &varId); |
| ProcessLoad(varId); |
| }); |
| } |
| // If function parameter, treat as if it's result id is loaded from |
| else if (liveInst->opcode() == SpvOpFunctionParameter) { |
| ProcessLoad(liveInst->result_id()); |
| } |
| worklist_.pop(); |
| } |
| // Mark all non-live instructions dead, except branches which are not |
| // at the end of an if-header, which indicate a dead if. |
| for (auto bi = structuredOrder.begin(); bi != structuredOrder.end(); ++bi) { |
| for (auto ii = (*bi)->begin(); ii != (*bi)->end(); ++ii) { |
| if (IsLive(&*ii)) continue; |
| if (IsBranch(ii->opcode()) && |
| !IsStructuredIfHeader(*bi, nullptr, nullptr, nullptr)) |
| continue; |
| dead_insts_.insert(&*ii); |
| } |
| } |
| // Remove debug and annotation statements referencing dead instructions. |
| // This must be done before killing the instructions, otherwise there are |
| // dead objects in the def/use database. |
| for (auto& di : get_module()->debugs2()) { |
| if (di.opcode() != SpvOpName) continue; |
| if (KillInstIfTargetDead(&di)) modified = true; |
| } |
| for (auto& ai : get_module()->annotations()) { |
| if (ai.opcode() != SpvOpDecorate && ai.opcode() != SpvOpDecorateId) |
| continue; |
| if (KillInstIfTargetDead(&ai)) modified = true; |
| } |
| // Kill dead instructions and remember dead blocks |
| for (auto bi = structuredOrder.begin(); bi != structuredOrder.end();) { |
| uint32_t mergeBlockId = 0; |
| for (auto ii = (*bi)->begin(); ii != (*bi)->end(); ++ii) { |
| if (dead_insts_.find(&*ii) == dead_insts_.end()) continue; |
| // If dead instruction is selection merge, remember merge block |
| // for new branch at end of block |
| if (ii->opcode() == SpvOpSelectionMerge) |
| mergeBlockId = |
| ii->GetSingleWordInOperand(kSelectionMergeMergeBlockIdInIdx); |
| context()->KillInst(&*ii); |
| modified = true; |
| } |
| // If a structured if was deleted, add a branch to its merge block, |
| // and traverse to the merge block, continuing processing there. |
| // The block still exists as the OpLabel at least is still intact. |
| if (mergeBlockId != 0) { |
| AddBranch(mergeBlockId, *bi); |
| for (++bi; (*bi)->id() != mergeBlockId; ++bi) { |
| } |
| } else { |
| ++bi; |
| } |
| } |
| // Cleanup all CFG including all unreachable blocks |
| CFGCleanup(func); |
| |
| return modified; |
| } |
| |
| void AggressiveDCEPass::Initialize(ir::IRContext* c) { |
| InitializeProcessing(c); |
| |
| // Clear collections |
| worklist_ = std::queue<ir::Instruction*>{}; |
| live_insts_.clear(); |
| live_local_vars_.clear(); |
| dead_insts_.clear(); |
| |
| // Initialize extensions whitelist |
| InitExtensions(); |
| } |
| |
| Pass::Status AggressiveDCEPass::ProcessImpl() { |
| // Current functionality assumes shader capability |
| // TODO(greg-lunarg): Handle additional capabilities |
| if (!get_module()->HasCapability(SpvCapabilityShader)) |
| return Status::SuccessWithoutChange; |
| // Current functionality assumes logical addressing only |
| // TODO(greg-lunarg): Handle non-logical addressing |
| if (get_module()->HasCapability(SpvCapabilityAddresses)) |
| return Status::SuccessWithoutChange; |
| // If any extensions in the module are not explicitly supported, |
| // return unmodified. |
| if (!AllExtensionsSupported()) return Status::SuccessWithoutChange; |
| // Process all entry point functions |
| ProcessFunction pfn = [this](ir::Function* fp) { return AggressiveDCE(fp); }; |
| bool modified = ProcessEntryPointCallTree(pfn, get_module()); |
| return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange; |
| } |
| |
| AggressiveDCEPass::AggressiveDCEPass() {} |
| |
| Pass::Status AggressiveDCEPass::Process(ir::IRContext* c) { |
| Initialize(c); |
| return ProcessImpl(); |
| } |
| |
| void AggressiveDCEPass::InitExtensions() { |
| extensions_whitelist_.clear(); |
| extensions_whitelist_.insert({ |
| "SPV_AMD_shader_explicit_vertex_parameter", |
| "SPV_AMD_shader_trinary_minmax", |
| "SPV_AMD_gcn_shader", |
| "SPV_KHR_shader_ballot", |
| "SPV_AMD_shader_ballot", |
| "SPV_AMD_gpu_shader_half_float", |
| "SPV_KHR_shader_draw_parameters", |
| "SPV_KHR_subgroup_vote", |
| "SPV_KHR_16bit_storage", |
| "SPV_KHR_device_group", |
| "SPV_KHR_multiview", |
| "SPV_NVX_multiview_per_view_attributes", |
| "SPV_NV_viewport_array2", |
| "SPV_NV_stereo_view_rendering", |
| "SPV_NV_sample_mask_override_coverage", |
| "SPV_NV_geometry_shader_passthrough", |
| "SPV_AMD_texture_gather_bias_lod", |
| "SPV_KHR_storage_buffer_storage_class", |
| // SPV_KHR_variable_pointers |
| // Currently do not support extended pointer expressions |
| "SPV_AMD_gpu_shader_int16", |
| "SPV_KHR_post_depth_coverage", |
| "SPV_KHR_shader_atomic_counter_ops", |
| }); |
| } |
| |
| } // namespace opt |
| } // namespace spvtools |